ext4: add read support for inline data

Let readpage and readpages handle the case when we want to read an
inlined file.
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/inline.c

@@ -454,6 +454,67 @@ static int ext4_destroy_inline_data_nolock(handle_t *handle,
 	return error;
 }
 
+static int ext4_read_inline_page(struct inode *inode, struct page *page)
+{
+	void *kaddr;
+	int ret = 0;
+	size_t len;
+	struct ext4_iloc iloc;
+
+	BUG_ON(!PageLocked(page));
+	BUG_ON(!ext4_has_inline_data(inode));
+	BUG_ON(page->index);
+
+	if (!EXT4_I(inode)->i_inline_off) {
+		ext4_warning(inode->i_sb, "inode %lu doesn't have inline data.",
+			     inode->i_ino);
+		goto out;
+	}
+
+	ret = ext4_get_inode_loc(inode, &iloc);
+	if (ret)
+		goto out;
+
+	len = min_t(size_t, ext4_get_inline_size(inode), i_size_read(inode));
+	kaddr = kmap_atomic(page);
+	ret = ext4_read_inline_data(inode, kaddr, len, &iloc);
+	flush_dcache_page(page);
+	kunmap_atomic(kaddr);
+	zero_user_segment(page, len, PAGE_CACHE_SIZE);
+	SetPageUptodate(page);
+	brelse(iloc.bh);
+
+out:
+	return ret;
+}
+
+int ext4_readpage_inline(struct inode *inode, struct page *page)
+{
+	int ret = 0;
+
+	down_read(&EXT4_I(inode)->xattr_sem);
+	if (!ext4_has_inline_data(inode)) {
+		up_read(&EXT4_I(inode)->xattr_sem);
+		return -EAGAIN;
+	}
+
+	/*
+	 * Current inline data can only exist in the 1st page,
+	 * So for all the other pages, just set them uptodate.
+	 */
+	if (!page->index)
+		ret = ext4_read_inline_page(inode, page);
+	else if (!PageUptodate(page)) {
+		zero_user_segment(page, 0, PAGE_CACHE_SIZE);
+		SetPageUptodate(page);
+	}
+
+	up_read(&EXT4_I(inode)->xattr_sem);
+
+	unlock_page(page);
+	return ret >= 0 ? 0 : ret;
+}
+
 int ext4_destroy_inline_data(handle_t *handle, struct inode *inode)
 {
 	int ret;

fs/ext4/inode.c

@@ -649,6 +649,9 @@ static int _ext4_get_block(struct inode *inode, sector_t iblock,
 	int ret = 0, started = 0;
 	int dio_credits;
 
+	if (ext4_has_inline_data(inode))
+		return -ERANGE;
+
 	map.m_lblk = iblock;
 	map.m_len = bh->b_size >> inode->i_blkbits;
 
@@ -2687,6 +2690,12 @@ static sector_t ext4_bmap(struct address_space *mapping, sector_t block)
 	journal_t *journal;
 	int err;
 
+	/*
+	 * We can get here for an inline file via the FIBMAP ioctl
+	 */
+	if (ext4_has_inline_data(inode))
+		return 0;
+
 	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) &&
 			test_opt(inode->i_sb, DELALLOC)) {
 		/*
@@ -2732,14 +2741,30 @@ static sector_t ext4_bmap(struct address_space *mapping, sector_t block)
 
 static int ext4_readpage(struct file *file, struct page *page)
 {
+	int ret = -EAGAIN;
+	struct inode *inode = page->mapping->host;
+
 	trace_ext4_readpage(page);
-	return mpage_readpage(page, ext4_get_block);
+
+	if (ext4_has_inline_data(inode))
+		ret = ext4_readpage_inline(inode, page);
+
+	if (ret == -EAGAIN)
+		return mpage_readpage(page, ext4_get_block);
+
+	return ret;
 }
 
 static int
 ext4_readpages(struct file *file, struct address_space *mapping,
 		struct list_head *pages, unsigned nr_pages)
 {
+	struct inode *inode = mapping->host;
+
+	/* If the file has inline data, no need to do readpages. */
+	if (ext4_has_inline_data(inode))
+		return 0;
+
 	return mpage_readpages(mapping, pages, nr_pages, ext4_get_block);
 }
 
@@ -3078,6 +3103,10 @@ static ssize_t ext4_direct_IO(int rw, struct kiocb *iocb,
 	if (ext4_should_journal_data(inode))
 		return 0;
 
+	/* Let buffer I/O handle the inline data case. */
+	if (ext4_has_inline_data(inode))
+		return 0;
+
 	trace_ext4_direct_IO_enter(inode, offset, iov_length(iov, nr_segs), rw);
 	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
 		ret = ext4_ext_direct_IO(rw, iocb, iov, offset, nr_segs);

fs/ext4/xattr.h

@@ -139,6 +139,8 @@ extern int ext4_prepare_inline_data(handle_t *handle, struct inode *inode,
 extern int ext4_init_inline_data(handle_t *handle, struct inode *inode,
 				 unsigned int len);
 extern int ext4_destroy_inline_data(handle_t *handle, struct inode *inode);
+
+extern int ext4_readpage_inline(struct inode *inode, struct page *page);
 # else  /* CONFIG_EXT4_FS_XATTR */
 
 static inline int
@@ -255,6 +257,11 @@ static inline int ext4_destroy_inline_data(handle_t *handle,
 {
 	return 0;
 }
+
+static inline int ext4_readpage_inline(struct inode *inode, struct page *page)
+{
+	return 0;
+}
 # endif  /* CONFIG_EXT4_FS_XATTR */
 
 #ifdef CONFIG_EXT4_FS_SECURITY